Geophysical Survey Systems, Inc.
SIR® 4000
Manual
MN72-433 Rev F
57
Process Menu
1
Gain Mode and Edit Gain Curve:
The thin, red line superimposed over the scan in the O-Scope
window is the gain curve. The centerline of the scan is zero and to the left of it is negative (decreasing
gain) and the right is positive (increasing gain). Gain is applied in dB along an exponential function to
model signal loss. Your goal should be to have a gain curve that creates a scan trace with balanced
amplitude changes from top to bottom.
•
Select Auto Gain Mode:
If Auto Gain Mode is already selected you can press the Init
Command key at the bottom of the screen to apply an automatic gain curve to the current scan
trace. This will cause the system to re-initialize and add/subtract gain to produce a visible signal.
Drag the antenna over the area and look for evidence of clipping. If your data becomes clipped,
leave the antenna over the area where it is occurring and re-initialize by pressing the Init
Command key. This will decrease the gains so that the data will not clip.
•
If you plan to collect multiple profiles and wish to compare them, it is usually best to set the gain
to Manual Gain Mode, once you find gain settings which are workable (you can see targets and
the signal does not clip).
•
If you are performing real-time locating, then leaving the Gain Mode set to Auto will allow you
to use Init when your signal quality changes between profiles.
•
Edit Gain Curve:
If using Auto Gain Mode still leaves portions of the signal under-gained, you
can try increasing or decreasing the number of gain points. The number of gain points selected
are evenly distributed along the scan trace and changing the number of points can change where
along the scan trace amplification is increased or decreased.
o
Set Gain Mode to Manual.
o
Select Edit Gain Curve.
o
Add or erase point to modify the gain curve.
o
Save and Exit to return to the Collect Setup screen.
2
Static Stacking:
Point data is typically collected with some static stacking. A good default value
here is 64. The system will take 64 scans at each scan location and average them together to output a
single scan. This is done to minimize high-frequency, random noise.
Output Menu
1
Scale and Units:
Verify that you are using the appropriate vertical scale and units. The horizontal
scale will appear in number of scans during collection.
2
Spacing, Amplitude, and Fill:
Check that you are using your preferred display settings for Point
Mode.
Step 3 – Data Collection
1
To begin data collection press the green Start button one time. The screen will appear with one scan
trace on the left side of the data display screen and the rest of the data display will be blank.
2
Press the Next Point control button to collect subsequent scans. The Scan number will update in the
Information Bar at the top of the screen as additional scans are added.
3
At the end of your profile, press and hold the red Stop button for two seconds. If AutoSave is set to
On the profile will be saved and you will return to the Collect Setup menu. If AutoSave is set to Off a
system prompt will give you the option to save or discard the current file. Once an option has been
selected press and hold the red Stop button again and you will return to the Collect Setup screen.
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